During the production of fibers for paper making, wood or another fiber source is ground into chips and chemically and/or mechanically treated such that the chips may be broken down further and refined into individual fibers.
The actual production of fibers generally takes place inside a refiner. In the refiner, chips and other pre-fiber material are brought into contact with one or more rotating discs, such as those described in U.S. Pat. No. 2,156,321. The interaction of the wood or other cellulosic material with the refining rings of the refining discs causes the individual fibers contained within the cellulosic material to separate from one another.
Refiners may include a single rotating disc in close opposition to a stationary disc, or may involve two counter rotating discs. In either circumstance, however, it is important that the material introduced between the various refining discs be uniform in size, water content, and most importantly composition. For example, the introduction of rocks or metal into the gap between refining rings of the refining discs, along with cellulosic material to be processed, could dramatically reduce the useful life of the refining segments which make up the refining ring. This is particularly true when the cellulosic material used for the production of fiber contains a great deal of contaminants such as rocks, metal fragments, or other debris which have not, or cannot, be pre-separated.
Depending upon the size and throughput of the refiner, unwanted contaminants can ruin a refining disc in a matter of seconds, or at very least, reduce the normal life thereof. The costs of replacing the refining disc can run into thousands of dollars in parts alone. The time taken in replacing the disc and the lost production time caused thereby can dramatically increase the overall costs.
The present invention relates to a device which is designed to be associated with a refiner, either originally or as a retrofit, to protect the refining discs from contaminants.